The present invention relates to the use of silicon particles as a redox catalyst, an electrochemical device including the silicon particles and method thereof. It finds particular application in conjunction with a redox catalyst, an energy-generation device such as a fuel cell, a sensor, an electrochemical reactor, and a memory, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Fuel cell technology is viewed as an increasingly important alternative means for generation of energy. To utilize nature's renewable energy sources such as various kinds of organic fuel, new electrocatalysts, especially those with novel properties due to their dimensions on the nanoscale, need to be developed in order to meet the requirements imposed by fuel cell applications, as described in D. R. Rolison, Science 299, 1698 (2003); M. Valden, X. Lai, D. W. Goodman, Science 281, 1647 (1998); A. S. Arico, P. Bruce, B. Scrosati, J.-M. Tarascon, W. V. Schalkwijk, Nature Materials 4, 366 (2005); and G. Che, B. B. Lakshmi, E. R. Fisher, C. R. Martin, Nature 393, 346 (1998).
Platinum-based noble metals are currently used in commercial fuel cells as the anode material to achieve electro-catalysis (electro-oxidation) of methanol and ethanol. Publications such as W. Vielstich, H. A. Gasteiger, A. Lamm, Eds., Handbook of fuel cells—fundamentals, technology and applications, vol. 2 (John Wiley & Sons, 2003), pp and E. Reddington et al., Science 280, 1735 (1998) have disclosed the use of bimetallic electrocatalyst systems based on rare/precious metals such as the platinum-ruthenium (Pt—Ru) alloy, which have been widely used as the anode electrode for direct electro-oxidation of methanol in direct methanol fuel cells. According to M. Watanabe, S. Motoo, J. Electroanal. Chem. 60, 259 (1975), the binary alloys offer a “bi-functional mechanism”, in which Pt breaks the C—H bonds of methanol and Ru promotes water discharge and removes adsorbed CO species in order to reduce electrode poisoning.
Although fuel cells based on binary alloys are commercially available, the high cost of precious metals and their limited supply make this kind of fuel cell economically unviable, as realized by S. G. Chalk, J. F. Miller, Journal of Power Sources 159, 73 (2006). Moreover, the acute and chronic toxicity of Ruthenium is not fully known. However, since oxidation of Ruthenium forms the highly toxic and volatile ruthenium oxide, the portable use and disposal of the alloy-based fuel cells will cause safety and environmental concerns. In addition, electrode poisoning is also a major problem affecting the performance of present fuel cells.
Enzymes are used for the construction of sensors. However, enzymes are not only expensive; their stability is also a major problem for long-term implantable applications.
Advantageously, the present invention provides the use of silicon particles as a redox catalyst, an electrochemical device comprising the silicon particles and method thereof, which overcome the afore-mentioned problem. For example, the electrochemical device uses silicon particles which are inexpensive and non-poisonous; and it uses particle-immobilized electrode that does not induce electrode poisoning.